The role of Peptides in Cosmetics
Reviewed by Dr Mohammad Baghaei
Description of peptides
Like proteins, peptides are large biological molecules with molecular weight up to 10 kDa. Peptides are made of amino acid linked into linear chain with overall length is up to 100 amino acids. Nowadays, many scientists descripe peptides as a polypeptide chains with up to 50 amino acids. It is difficult to unambiguously classify peptides and proteins, especially for long peptides and small proteins. One of the most reasonable classification is based on the structural flexibility. According to this classification peptides are flexible polypeptide chains without one preferable conformation, whereas proteins maintain some preferable conformation, at least for the core residues. According to this classification, 51 amino acid insulin is a protein with the core structure fixed by three disulphide bridges.
Peptide classification by function of peptides
Peptides are involved into many processes in the living organisms and it is possible to classify them on the basis of their function. As usually this classification is not perfect because some of the peptides can belongs to different groups simultaneously, for example, oxytocin can be considered as a hormone (transmitting signal between cells) and also oxytocin can be classified as neuropeptide because ther function as neurotransmitter in the brain.
- Hormones. Hormones are involved into carrying signals between cells. Classical examples of hormones are: bradykinins, gastrins, oxytocins etc.
- Neuropeptides. Neuropeptides found in neural tissues. usually these peptides are produced in the brain and involved into regulatory and signalling processes. Classical examples of neuropeptides are: endorphins, vasopressin, atrial-natriuretic peptide etc.
- Alkaloids. Alkaloids are peptides, usually from plants, fungi and some animals like shellfish. Alkaloids involved into defend of one organism from consuming by other organisms. Classical examples of peptide alkaloid are: ergotamine, pandamine, dynorphin A-(1-8)-octapeptide, N beta-(D-Leu-D-Arg-D-Arg-D-Leu-D-Phe)-naltrexamine, etc.
- Antibiotics. Antibiotics are inhibits the grows of micro organisms, usually bacterial cells and locationally fungi and protozoa. Classical examples of peptide antibiotics are: tyrothricinm bacitracin, gramicidin, valinomicin etc.
- Toxins. Toxin is the poison substance. Peptide toxins are the most poison substances. Examples of peptide toxins are: palutoxins, agatoxins, curtatoxins etc.
- Regulation peptides. The group of regulation peptides is not well defined because almost any peptides can regulate some processes in organisms, but this group is used to classify peptides which are not clearly belongs to other groups. examples of regulatory peptides are: anserine, carnosine, etc.
Peptide classification by synthesis
Sometimes peptides can be classified by their synthesis type.
- Ribosomal peptides. Ribosomal peptides (almost all known peptides) are synthesized by translation of mRNA on ribosomes. Usually they subjected to further postranslational modification; which can involve even recemization of L-amino acids to D-amino acids.
- Nonribosomal peptides. Nonribosomal peptides (glutathione cyclopeptides etc.), are synthesized during enzymatic catalysis
- Peptones. Peptones are peptides derived from digestion processes.
· Peptide synthesis
· Peptide synthesis is a chemical process of coupling of the carboxyl group of one amino acid to the amino group of another amino acid. Usually chemical techniques are used to synthesize peptides of up to 30-40 amino acids length. The fist peptide synthesis was carries out by T. Curtius 1882 via reaction between benzyl cloride and silver salt of glycine. During this process Curtius produce crystals of N-benzyl-glycile-glycine. The first pure di-peptide (Gly-Gly) was synthesized by E. Fischer in 1901.
In 1932, Bergmann from Fisher's lab discover carbobenzoxy group C6H5CH2OCO which is very convenient as a protective group for peptide synthesis. In 1950-1960 the first biological peptides, like oxytocin, vasopressin, insulin and others were synthesized.
· Types of peptide synthesis
· Peptide synthesis process can be classified on the basis of used techniques and type of the final product.
- Liquid-phase peptide synthesis. Liquid-phase or classical peptide synthesis can be devided into two classes - step-by-step peptide synthesis with subsequent adding of one amino acid at ones from C-terminal to N-terminal and block-synthesis with coupling of polypeptide fragments. Liquid-phase peptide synthesis is used in large-scale peptide production for industry.
- Solid-phase peptide synthesis. Solid-phase peptide synthesis is a process during which the polypeptide chain is covalently bound via linker to the porous insoluble beds particles. Each cycle of this solid-phase peptide synthesis can be described in few steps - deprotection of N-terminal group, coupling with N-protected amino acid. The standard repetitious step allows to use robotic equipment for this type of synthesis. Solid-phase peptide synthesis is perfect for researche laboratories and small quantities of production.
- Homo-polymerisation. Homo-polymerisation is used to synthesize homo-polymeric chains of amino acids.
- Enzymatic peptide synthesis. Enzymatic peptide synthesis is based on enzymes which are able to formate peptide bond. Unfortunately this technique is very complicated and there is no remarkable result was achieved yet.
- Partial peptide synthesis. In partial peptide synthesis technique the natural peptides and proteins are used as a source of peptide fragments.
- Cyclopeptide synthesis. Cyclopeptide synthesis is the cyclization of linear peptides.
- Non-standard peptide synthesis. Non-standard peptide synthesis is used to produce peptides with non-standard peptide bonds, for example ester-bonds etc.
Skin Aging & Peptides
· Ageing is universal but complex biological process with proverbial and unambiguous manifestations characterized by impairment of various functions and decreased ability to respond stress. It is also accompanied by syndrome of changes and has been a concern of every society. Scientific language that describes human ageing also vacillate, it struggles to differentiate ageing from disease, healthy ageing from unhealthy ageing, and optional ageing from obligatory ageing and whether growing old is pathological or physiological. According to WHO in 2000, there were 600 million people aged 60 and over; there will be 1.2 billion by 2025 and 2 billion by 2050. In the developed world, the very old (age 80+) is the fastest growing population group. The proportion of the population made up of elderly persons in the United States is projected to increase from 13 to 20 percent of the population in 2000 to 2030.
· The desire to look young and in turn vital has been a lure to man since ancient times, though aging as a rule remains a fact of life. The current advances in health sciences have lead to a boost in average life expectancy; hence, aging skin has set to become an issue to the current dermatologists. Increasing awareness regarding skin research has lead dermatologists and common man alike to seek out for answers concerning the complexities of the aging process.
· Biologists define aging as a genetic physiological process associated with morphological and functional changes in cellular and extracellular components aggravated by injury throughout life and resulting in a progressive imbalance of the control regulatory systems of the organism, including hormonal, autocrine, neuroendocrine, and immune homeostatic mechanisms In short, aging is a process in which both intrinsic and extrinsic determinants lead progressively to a loss of structural integrity and physiological function. The theories of aging are defined as following:
· The theories of aging are defined as following:
Cross-linking theory of aging
The cross-linking hypothesis is based on the observation that with age, our proteins, DNA, and other structural molecules develop inappropriate attachments or cross-links to one another. These unnecessary links or bonds decrease the mobility or elasticity of proteins and other molecules. Proteins that are damaged or no longer needed are normally broken down by enzymes called proteases, and the presence of cross-linkages inhibits the activity of proteases. These damaged and unneeded proteins, therefore, stick around and can cause problems.
One of the main ways cross-linking occurs is through a process called glycosylation or glycation. Glucose molecules can stick to proteins, then transform into a brownish molecule called an advanced glycosylation endproduct, or AGE. When both of the sticky ends of AGEs adhere to neighboring proteins, they form permanent, disabling cross-links. Some research supports the hypothesis that cross-linking contributes to aging. Cross-linking of the skin protein collagen has been shown to be at least partly responsible for wrinkling and other age-related changes in skin. Cross-linking of proteins in the lens of the eye is also believed to play a role in age-related cataract formation. Researchers speculate that cross-linking of proteins in the walls of arteries or the filtering systems of the kidney account for at least some of the atherosclerosis (hardening of the arteries) and age-related decline in kidney function observed in older adults. Another study conducted at the Bjorksten Institute in Wisconsin treated brain tissue from young animals with known cross-link-inducing compounds. That brain tissue soon looked quite similar to older brain tissue with its naturally cross-linked brain proteins, adding evidence in support of this theory of aging.
· Wear and tear theory of aging
Years of damage to cells, tissues, and organs wear them out, killing them, and then the body. Telomerase the cap of DNA shortens with each cell division and reaches critical short length beyond which cell cannot divide and becomes senescent.
· Free radical theory of aging
The free-radical theory of aging (FRTA) states that organisms age because cells accumulate free radical damage over time. A free radical is any atom or molecule that has a single unpaired electron in an outer shell. While a few free radicals such as melanin are not chemically reactive, most biologically-relevant free radicals are highly reactive. For most biological structures, free radical damage is closely associated with oxidative damage. Antioxidants are reducing agents, and limit oxidative damage to biological structures by passivating free radicals.
Strictly speaking, the free radical theory is only concerned with free radicals such as superoxide ( O2- ), but it has since been expanded to encompass oxidative damage from reactive oxygen species such as H2O2, or OH-.
Denham Harman first proposed the free radical theory of aging in the 1950s, and in the 1970s extended the idea to implicate mitochondrial production of reactive oxygen species.
Somatic mutation theory of aging
The Somatic Mutation Theory of Aging is one of several well developed theories that attempt to explain why human bodies age. Logically, it does not make sense that the same body that produces billions of cells from the age of 0 to about 27 suddenly begins to lose the ability to produce new cells that are as vital and strong as they have always been. The mechanism of reproduction does not change. The general cellular structure does not change. For the most part, the vast majority of your cells continue to do this quite well for another 20 or 30 years. But, everyone eventually knows that the aging process catches up with them.
The pacemaker theory of aging
certain organs or organ systems (eg, the immune and neuroendocrine systems, notably the hypothalamus) are thought to be intrinsic pacemakers of the aging process, genetically programmed to involute at specific times during an organism’s life span. This programmed senescence is hypothesized to affect the aging of the entire organism.
The DNA & Genetic Theories
some scientists regard this as a Planned Obsolescence Theory because it focuses upon the encoded programming within our DNA. Our DNA is the blueprint of individual life obtained from our parents. It means we are born with a unique code and a predetermined tendency to certain types of physical and mental functioning that regulate the rate at which we age.
But this type of genetic clock can be greatly influenced with regard to its rate of timing. For example, DNA is easily oxidized and this damage can be accumulated from diet, lifestyle, toxins, pollution, radiation and other outside influences.
Thus, we each have the ability to accelerate DNA damage or slow it down.
One of the most recent theories regarding gene damage has been the Telomerase Theory of Aging. First discovered by scientists at the Geron Corporation, it is now understood that telomeres (the sequences of nucleic acids extending from the ends of chromosomes), shorten every time a cell divides. This shortening of telomeres is believed to lead to cellular damage due to the inability of the cell to duplicate itself correctly. Each time a cell divides it duplicates itself a little worse than the time before, thus this eventually leads to cellular dysfunction, aging and indeed death.
Biological Markers of Aging
These are measurable indicators of aging and they include in vitro proliferative capacity of fibroblast, glycation of collagen, and DNA unwinding rate.
Chronologically aged skin is thin, relatively flattened, dry and unblemished with some loss of elasticity and age-related loss of architectural regularity. General atrophy of the extracellular matrix is reflected by a decrease in the number of fibroblasts. Reduced levels of collagen and elastin, with impaired organization are primarily because of decreased protein synthesis affecting types I and III collagen in the dermis, with an increased breakdown of extracellular matrix proteins. Aging happens due to a variety of reasons.
These are as following:
- Constant effect of gravity on soft tissue results in their sagging over the facial skeleton.
- Sun damage to skin.
- Hormonal changes in women around menopause.
- Decreased skin blood flow associated with aging.
- Weight gain due to slow down of metabolism and fat deposition in regions of body called 'depots'.
- Fascial and ligament laxity.
- Shrinkage of glandular tissue (Salivary glands).
- Skeletal resorption.
There are two types of aging, intrinsic aging and extrinsic aging. Intrinsic aging is the slow irreversible degeneration of tissue that affects almost all body organs. Intrinsic or natural aging is cellularly determined as a function of heredity, is inevitable, and results in cutaneous alterations.The rate of aging is significantly different among different populations, as well as, among different anatomical sites even within a single individual. The intrinsic rate of skin aging in any individual can also be dramatically influenced by personal and environmental factors, particularly the amount of exposure to ultraviolet light.
The common signs of intrinsic skin aging are:
- Fine wrinkles
- Thin and transparent skin
- Loss of underlying fat leading to hollowed cheeks and eye sockets with noticeable loss of firmness on the hands and neck
- Bones shrink away from the skin as a result of bone loss, which causes sagging skin
- Dry skin with pruritus
- Inability to sweat sufficiently to cool the skin
- Greying hair eventually turning white.
Skin that age intrinsically is smooth and unblemished, and characterized by normal geometric patterns, with some exaggerated expression lines. Histologically, such skin manifests epidermal and dermal atrophy, flattening of the epidermal rete ridges, as well as reduced numbers of fibroblasts and mast cells. In addition, increases are seen in the number of collagen fibrils as well as the ratio of collagen III to collagen I.
Intrinsic Aging Determinants
The factors involved in determining intrinsic aging are as follows.
Ethnicity
The greatest effect of ethnicity on aging is primarily related to differences in pigmentation. High levels of pigmentation are protective with regard to the cumulative effects of photoaging, with African-Americans showing little cutaneous difference between exposed and unexposed sites. Basal cell carcinoma and squamous cell carcinoma occur almost exclusively on sun-exposed skin of light-skinned people. African-American skin is more compacted than Caucasian skin, as well as having a higher intercellular lipid content, which may contribute to more resistance to aging.
Anatomic variations
Skin rigidity is much higher at the forehead than at the cheek in post-menopausal women. Also, in areas of the body with high blood flow, for example, lip, finger, nasal tip, and forehead, blood flow decreased with age compared to areas with baseline low blood flow, in which no difference was observed. The decrease in epidermal thickness with aging was found to be smaller at the temple than at the volar forearm, which may be the effect of cumulative photo aging.
Hormonal influence
Hormonal changes in skin are primarily the effect of changes of oestrogen levels in the skin especially in women. After menopause, the following changes occur: vaginal epithelium atrophies, cervico-vaginal secretions become sparse, vaginal pH rises, atrophic vaginitis becomes more common, collagen and water content decrease, pubic hair grays and becomes sparse, the labia majora loses subcutaneous fat and also the labia (labia minora, vestibule and vaginal mucosa) atrophies. The cumulative effect of oestrogen deficiency contributes to poor wound healing. Skin collagen content and thickness decrease with the hormonal affects of castration. Also dramatic hormonal changes, particularly thyroid, testosterone and oestrogen, alter epidermal lipid synthesis.
Extrinsic Aging Determinants
Extrinsic factors are, to varying degrees, controllable and include exposure to sunlight, pollution or nicotine, repetitive muscle movements like squinting or frowning, and miscellaneous lifestyle components such as diet, sleeping position and overall health.
Sun exposure
When skin is exposed to sunlight, UV radiation is absorbed by skin molecules that can generate harmful compounds, called reactive oxygen species (ROS), which then cause "oxidative damage" to cellular components like cell walls, lipid membranes, mitochondria, and DNA. These ROS also play an important role in molecular pathways. UV-B is a strong immunosuppressive agent and therefore may have very significant systemic effects related to the release of immunologically active molecules from the skin, such as tumour necrosis factor (TNF)-alpha and cis-urocanic acid, which themselves produce immunosuppressive effects including depression of delayed hypersensitivity, suppression of T-lymphocytes and activation of cutaneous herpes simplex infections.
Photoaged skin is classified according to the Glogau score and the degree of wrinkling observed as:
- Mild (age 28-35 years): Few wrinkles, no keratoses
- Moderate (age 35-50 years): Early wrinkling, sallow complexion with early actinic keratoses
- Advanced (age 50-60 years): Persistent wrinkling, discolouration of the skin with telangiectases and actinic keratoses
- Severe (age 65-70 years): Severe wrinkling, photoaging, gravitational and dynamic forces affecting the skin, actinic keratoses with or without skin cancer.
Life style influence
Skin is affected by ambient conditions such as temperature and humidity. An increase in skin temperature of 7-8°C doubles the evaporative water loss. Low temperature stiffens skin and decreases evaporative water loss even with plenty of humidity in air, as structural proteins and lipids in the skin are critically dependent on temperature for appropriate conformation.
Effects of smoking
Tobacco smoking in addition to seriously affecting the internal organs of the body, affects a person's appearance by altering the skin and body weight and shape. Skin damaged by smoke appears grey and wasted. Cigarette smoking is strongly associated with elastosis in both sexes, and telangiectasia (red spots on skin) in men. Smoking causes skin damage primarily by decreasing capillary blood flow to the skin, which, in turn, creates oxygen and nutrient deprivation in cutaneous tissues. It has been shown that those who smoke have fewer collagen and elastin fibres in the dermis, which causes skin to become slack, hardened and less elastic. It has been suggested that MMP-1 induced by smoking may explain the multiplicative effects of sunlight and smoking.
Effects of pollution
Despite its barrier properties, the skin is also a point of entry for substances capable of causing harm, e.g. exposure to xenobiotics, pesticides, topical drugs and cosmetics
PEPTIDES
The population demographic shift in the world calls for increased efforts to prevent the aging process and develop safe and effective drugs for elderly. In cosmetic dermatology, experts are exploring better anti-solar, anti ageing, anti wrinkle and firming products. Pharmaceutical companies frequently use peptides as active ingredients in their creams. Peptides have different effects on the skin especially for cosmetics purposes, but one important hurdle to use them topically is their permeability to penetrate skin.
Generally, permeation ability depends on different factors:
1. physicochemical properties of the substance (acid dissociation constant {pKa},
2. molecular size,
3. stability,
4. binding affinity,
5. solubility and partition coefficient);
6. the time- scale of permeation;
7. integrity,
8. thickness and components of the skin,
9. cutaneous metabolism;
10. site, area and duration of application;
11. properties of transdermal device and creation of a local depot at the site of application .
In summary, it is ideal to have a topical drug with parameters within the below mentioned listed range:
- Molecular weight less than 500 Da;
- Moderate log of partition coefficient octanol/water between 1 and 3;
- Melting point less than 200 c ;
- Reasonable aqueous solubility(>1mg Ml -1);
- No or few polar centers.
Diffusivity of the molecules in stratum corneum is related to the size and number of hydrogen bonding groups on a molecule, being maximal for small non-hydrogen bonding molecules and reaching a minimum with about 4 hydrogen bonding groups.
As peptides and proteins contain many amide bonds, (as hydrogen bond donor and acceptor groups), and because of their large molecular size, they have low diffusivity in skin. Furthermore as they often charged at physiological pH, they are intrinsically hydrophilic. Hence, the lipophilic stratum corneum is a significant barrier to penetration.
Overall, topical peptides and proteins have been successfully and widely used. Patch test to purified protein derivatives tuberculin protein and more specific derivatives like MPB64 have been effectively addressed for active tuberculosis diagnosis.
Tacrolimus and with lower permeability, pimecrolimus can penetrate through the skin to treat atopic dermatitis pations.
Frech et al. Found a safe and protective vaccine patch containing heat-labile protein enterotoxin to prevent diarrhoea in travelers to Mexico and Guatemala. Even topical cyclosporine A with molecular weight of more than 1200 Da could be delivered into the skin with delivery enhancing methods.
The main barrier for topical drugs is stratum corneum, the outermost layer of epidermis. Several techniques overcome such a barricade. For example, chemical penetration enhancers might be useful for peptide dermal delivery.
One study addressed usefulness of iontophoresis for topical insulin application. Other mechanisms like sonophoresis in liposomal peptides and colloidal carrier systems are considered helpful in this regard. Carrier peptides can increase and accelerate the permeation process. Chen et al. reported that a short synthetic peptide (ACSSSPSKHCG) identified by in vivo phage display assay, facilitated efficient transdermal insulin delivery through intact skin. Although topical use of a peptide has potential to be effective, delivery across skin can be difficult because of the ionic nature of such materials. An approach to improving delivery is the use of fatty acid derivatives to increase the lipophilic property of the peptide.
For example, the palmitoyl derivative of the polypeptide interferon alpha penetrates across human skin five – to six- fold greater than the simple peptide and also, facial skin improvement has been reported after topical pal-KTKS (palmitoyl pentapeptide-4) therapy.
Many peptides and proteins used for cosmetic indications; glycyl-histidyl-lysine (GHK)-Cu is one of the most widely utilized for wound healing and anti- ageing indications. Abdulghani et al. revealed its enhanced but insignificant anti- ageing effects when compared with tretinoin, Vitamin C and melatonin.
Palmitoyl KTTKS, the other frequently used peptide was shown to have more significant results than placebo and an active comparator.
Clinical studies for palmitoyl pentapeptide-4 had promising results. The depth of wrinkles was reduced more than 44.9% vs. 4.3% increase for placebo after 2 month
Cosmetic topical peptide can be categorized into 4 groups:
1- Signal peptides
2- Enzyme inhibitor peptides
3- Neurotransmitter- inhibitor peptides and
4- Carrier peptides.
SIGNAL PEPTIDES
Signal peptides stimulate matrix protein production in general and collagen synthesis in specific. They may be accomplished by stimulation and growth of different skin cells like human skin fibroblasts. Signal peptides can also increase elastin, protoglycan, glycosaminoglycans and fibronectin proliferation. By increasing matrix cell activities and consequently collagen production, the skin looks firmer and younger. The tripeptide -1 (glycyl- L-histidyl- L-lysin or GHK) is primarily known as carrier peptides. It mainly helps to stabilize and deliver Cu. Carrier peptides are discussed later. However, GHK was originally isolated from human plasma in 1973 by Pickart and Thaler and its wound repair properties were observed in 1985 by Maquart et al. in 1999. Maquart et al. concluded that GHK or its Cu complex functioned as an activator of tissue remodeling .it is also a signal peptide that promotes extra large collagen aggregates degradation in scars, regular collagen synthesis in normal skin, Elastin , Proteoglycans and Glycosaminoglycans production, growth rate and migration of different cell types and inflammatory and anti oxidant responses.
In a controlled ex vivo study, Biotinyl-GHK and vehicle were investigated. Biotinyl –GHK but not vehicle solution showed stimulation of collagen IV, laminin production and keratinocyte mitosis.
Tripeptide-1 can be also conjugated with palmitic acid and form pal-tripeptide-1(Biopeptide-CL). In vitro and in vivo studies approved that Biopeptide-CL stimulates collagen and glycosaminoglycans synthesis.
Pal-KTTKS(palmitoyl pentapeptide-4), a synthetic signal peptide from pro–collagen I fragment, stimulates collagen I,III and VI and also fibronectin , elastin and glycosaminoglycan production and has been frequently used as anti ageing or anti- wrinkle agents. In a study on 93 Caucasian female volunteers, Pal- KTTKS had significantly better scores than placebo for expert grader assessment and subject self-assessment of age hyper pigmented spots. Osborne et al. showed a robust result for this peptide in reducing bumpy texture and fine wrinkles compared with other baseline and comparators.
Palmitoyl oligopeptide (Pal-GHK) consists of a short chain of three amino acids (a.k.a. GHK peptide or glycine-histidine-lysine) connected to palmitic acid. Palmitic acid is a fatty acid added to improve the peptide's oil solubility and thus skin penetration. The peptide GHK is a fragment of type I collagen molecule and is believed to serve as a biological indicator of increased degradation of the skin matrix. Indeed, when collagen is degraded, more of its small fragments get created in the body, including GHK. Furthermore, GHK is believed to stimulate the feedback loop triggering the synthesis of new collagen as well as other components of the skin matrix. When the key skin matrix-producing cells (fibroblasts) detect increased levels of GHK, they "assume" that the skin matrix is being lost at a higher rate and begin synthesizing it more vigorously. Thus, Pal-GHK (a version of GHK designed for better skin penetration) is intended to stimulate skin matrix replenishment via topical application, leading, presumably, to wrinkle reduction, skin firming and other benefits.
Palmitoyl tetrapeptide-7 consists of a short chain of four amino acids (a.k.a. GQPR peptide or glycine-glutamine-proline-arginine) connected to palmitic acid. Palmitic acid is a fatty acid added to improve the peptide's oil solubility and thus skin penetration. Palmitoyl tetrapeptide-7 is believed to work by reducing the production of interleukin-6 (IL-6) by the key skin cells, keratinocytes and fibroblasts. IL-6 is a molecule that promotes inflammation, which, in turn, leads to faster degradation of the skin matrix and thus contributes to the development of wrinkles and loss of skin firmness and elasticity. By reducing the levels of IL-6 and possibly other inflammation mediators, Palmitoyl tetrapeptide-7 is thought to slow down the degradation of the skin matrix and may also stimulate its replenishment.
Growth factor play an important role in reversing the ageing process on skin caused by extrinsic and intrinsic factors, although main use of growth factors is in wound healing. Recombinant human growth hormone has mitogenic effect on keratinocytes and fibroblasts and increases insulin growth factor-1 and sebum production.Cutaneous wound healing properties were confirmed by two trials on acute wounds.
Interferon alpha increases the concentration of dendritic cells and CD1a and HLA-DR positive cells . Ghersetich and Lotti conducted a before-after study with three different inclusion protocols: five individuals aged 18-21 years, five aged 57-75 years, and five underwent cycles of Psoralen + UVA(PUVA) therapy over a year and aged 30 -45 years. Alpha-interferon cream (2000000 IU per day) in carboxymethylcellulose and glycerin was applied on periauricular area three times a day for 4 weeks. Count for cells that expressed CD-1 and HLA-DR were significant compared with baseline only for aged and PUVA exposed volunteers (5+/-1.75 vs. 10+/- 4.47 and 6 +/- 3.18 vs. 16+/-2.15 for aged group and 4 +/- 3.47 vs. 10+/-3.53 and 3 +/- 3.12 vs. 14+/- 1.75 for PUVA group respectively).
Transforming growth factor alpha and beta are growth factors that reversibly inhibit keratinocytes migration, chemotatic for macrophages and fibrobalsts among major growth factor, transforming growth factor (TGF) Alpha has the highest human keratinocyte pro-motility activity, reaching nearly 80% of the activity in serum.
Heat shock proteins involve in one of the principal mechanisms of cell defense and protection from stress. Among its family, Hsp 70 has protective effects against UV, apoptosis and ischemia and recommended for wound healing and anti ageing uses. Hsp 70 can effectively inhibit aggregation and assist in the refolding of denatured proteins. It can reduce cellular damage by retaining the damaged proteins in soluble form, as well as by binding to unfolded or misfolded proteins to assist in their proper refolding.
Keratin is a major protein in the structure of hair and skin that can be extracted from human hair or sheep's wool. Keratin's topical application can improve hydration and elasticity of the skin and hair. It is commonly used in skin and hair moisturizers, firming agents and hair shiners.
Barba et al. conducted a randomized trial comparing 3% Keratin peptides with dionized water and untreated control in 16 healthy female. Keratin peptides were effective on disturbed but not undisturbed skin.
Enzyme inhibitor peptides
Enzyme inhibitor peptides directly or indirectly inhibit an enzyme. Soybean protein (Soja protein) or peptide, enzyme inhibitor peptides naturally extracted from soybean seeds, inhibits the formation of proteinases. soy protein is frequently used as a anti-ageing, skin moisturizer, anti- solar, cleansing detergent and hair- promoting agent, in a randomized, double-blind, placebo-controlled study, soy extract and placebo creams were applied to volar forearm of 21 healthy women. Papillae index was increased more by soy extract than placebo (3.76 vs. 4.56 in arbitrary units, p<0.05). Another study with pseudo-randomized design in 10 Caucasian females concluded the superiority of 2% soya biopeptide emulsion to placebo, in terms of collagen and stimulation of glycosaminoglycan contents.
Another enzyme inhibitor protein (silk protein, sericin), naturally extracted from Moddle silk gland of the silkworm Bombyx Mori, has antioxidant properties with high affinity to chelate with cu. In addition, it inhibits lipid peroxidation and tyrosinase activity and Keratinocyte apoptosis. In a within-patient untreated-controlled study, 0.2 g Sericin gel was compared with untreated site with hydroxyproline assay and TWEL measurement to evaluate its hydrating effect, for hydroxyproline assay, Sericin gel was applied on the dried skin of the forearm at the test site. For TWEL, the upper portion of forearm was used as the application site of sericin gel and lower portion of forearm for control. Although hydroxypropline content was slightly promising in all related parameters for sericin, no significant differences in hydroxyproline content, skin impedance and TWEL contents were seen when compared with no treatment.
Neurotransmitter inhibitor peptide
Neurotransmitter inhibitor peptides inhibit acetylcholine release at the neuromuscular junction and have curare-like effect. Seven types (A-G) of botulinum toxin target peripheral cholinergic neurons where they selectively proteolyse synaptosome-associated protein of 25000 Da, syntaxin1 and synaptobrevin,the soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) proteins responsible for transmitter release, to cause neuromuscular paralysis but of different durations. Type A toxin proteolytically degrades the SNAP-25 protein, a type of SNARE protein. The SNAP-25 protein is required for the release of neurotranmitters from axon endings. Botulinum toxin type A (BXT-A) paralysis lasts longer (4-6 months) among botulinum toxin subtypes; make it a good choice for anti- wrinkle uses. Researchers have found less invasive topical equivalents of these toxins. Acetyl hexapeptide- 3 is a synthetic peptide that is especially marketed as a component of eyecare products and patterned from the N-terminal end of the protein SNAP-25 that inhibits SNARE complex formation and catecholamine release. Inhibition of noradrenaline and adrenaline release was also demonstrated. This small peptide exhibits the great advantage of its insignificant acute toxicity (2000 mg kg-1) as compared with BTX-A (20 ng kg-1).
Another open label vehicle-controlled trial, 10 % acetyl hexapeptide-3 and placebo creams were applied twice daily on 10 women and demonstrated a nearly 30% vs.10% improvement in periorbital
rhytids after 30 days as measured by silicone replica analysis respectively .
Pentapeptide-18 mimics the natural mechanism of enkephalins and as a result inhibits neuronal activity and catecholamine release. An active-controlled trial compared cream containing 5 % Pentapeptide-18, cream containing Acetyl hexapeptide- 3 and combination. Mean wrinkle reductions were 11.64% vs.16.26% vs. 24.62% for Pentapeptide-18, Acetyl hexapeptide- 3 and combination respectively. This study suggested a synergistic effect between Pentapeptide-18 and Acetyl hexapeptide- 3
Pentapeptide-3, a synthetic peptide that is a competitive Antagonist at the acetylcholine receptors safely blocks the sodium ion release at the synaptic membrane on muscles so they cannot contract as frequently.
Tripeptide-3 is used as an intensive anti- wrinkle agent and mimics the effect of Waglerin 1, a peptide that is found in the venom of the Temple Viper,Tropidolaemus Wagleri.
Carrier peptide
Carrier peptide belong to a general category that act as a facilitator of an important substance transportation, but their major application is to deliver important trace elements(like Cu and Mn) necessary for wound healing and enzymatic processes. Recently, several peptides and proteins have been developed to accelerate and facilitate the delivery of bioactive molecules into the skin. These peptides and proteins are known as penetrating peptides or membrane transduction peptides and have basic transduction domains in their structure.
A study demonstrated that short arginine-rich intracellular delivery peptides facilitate the transport of various proteins into living cells. Hou et al. also investigate whether arginine –rich peptide could serve as carriers for topical and /or transdermal drug delivery and concluded that protein penetration can be stimulated by such peptides even without fusion between carrier peptides and the protein. Another example of membrane transduction peptides is PEP-1 that can facilitate the penetration of an anti-ageing protein, ribosomal protein S3 (rpS3).
Abdulghani et al. conducted a non-randomized four-arm active controlled trial on 20 participants to compare GHK-Cu with topical tretinoin, Vitamin C and melatonin. Ten subjects received tretinoin and Vitamin C creams on the extensor surface of their right and left thighs respectively, for 1 month. Tretinoin, Vitamin C, melatonin and GHK-Cu increased pro- collagen synthesis in 4/10, 5/10, 5/10 and 7/10 of patients respectively.
GHK-Cu was tested in a 12 week placebo controlled study on facial skin of 71 women with mild to advanced photodamaged. By week 1 the active cream delivered significant improvement in skin laxity, clarity and overall appearance when compared with placebo. Significant improvement in fine lines was noted at week 2 and in wrinkles at week 4 over placebo. Significantly improved viscoelastic properties were consistent with ultrasound increase in overall skin density and thickness. Subjects indicated strong cream's performance acceptability. There were no adverse objective or subjective irritation findings.
BOTOX
BOTOX® contains a protein complex purified from the bacterium Clostridium botulinum. A component of this complex, Botulinum Toxin Type A is the important active ingredient. Type A is one of the seven distinct botulinum toxins produced by different strains of the bacterium. BOTOX® decreases muscle activity by blocking overactive nerve impulses that trigger excessive muscle contractions or glandular activity.i In addition, BOTOX® is believed to reduce neck pain associated with cervical dystonia through a temporary reduction in muscle activity and possibly through its influence on the pain sensory system (e.g., inhibiting the release of neurotransmitters involved in the transmission of painful sensations), although the exact mechanism of action is unknown.
Mechanism of Action
Phase I – Nerve‐Muscle Communication is Blocked
BOTOX® blocks the transmission of overactive nerve impulses to the targeted muscle by selectively preventing the release of the neurotransmitter acetylcholine (ACh) at the neuromuscular junction, temporarily preventing muscle contraction.i
This is primarily a local effect. In cervical dystonia, BOTOX® may also prevent the release of pain‐stimulating neuropeptides in peripheral nerves.
A) Binding:
The heavy chain portion of the active ingredient in BOTOX® (onabotulinumtoxinA) neurotoxin binds to the cell membrane of the motor nerve via an unidentified high‐affinity “acceptor” molecule. This high‐affinity binding action allows for efficient uptake of BOTOX® by the motor nerve and facilitates selective, targeted treatment at the injection site.
B) Internalizing:
After binding, the BOTOX® protein molecule passes through the cell membrane of the motor nerve and into its cytoplasm via a process called endocytosis. It is here that the enzymatic component (light chain) of the BOTOX® protein molecule is activated.
C) Blocking:
Inside the motor nerve, the light chain of the BOTOX® (onabotulinumtoxinA) protein molecule cleaves apart a protein (called SNAP25) that enables vesicles which store the neurotransmitter acetylcholine to attach to the cell membrane. Cleaving SNAP25 prevents these vesicles from fusing with the membrane and prevents the release of acetylcholine into the neuromuscular junction (the space between the motor nerve and the muscle). Thus, nerve impulses that control muscle contractions are blocked decreasing muscle activity.
Cleaving SNAP25 also blocks release of neuropeptides involved in the transmission of painful sensations (including substance P, glutamate and calcitonin gene‐related peptide, or CGRP), theoretically reducing pain sensitization of peripheral nerves. This may be how BOTOX® reduces the neck pain associated with cervical dystonia, although the exact mechanism of action is unknown.
Phase II – Nerve‐Muscle Communication is Restored
The effect of BOTOX® is generally temporary. Previous nerve impulse activity and associated muscle contractions resume over the course of a few to several months, depending on the individual patient and the indication for which they are being treated.
A) Nerve Sprouting:
New nerve endings sprout and connect to the muscle after the original nerve ending is blocked, renewing the ability of the nerve to cause muscle contractions.
B) Original Nerve Connection Re‐established:
Eventually, the new nerve sprouts retract and the original nerve ending regains its function, suggesting that treatment with BOTOX® (onabotulinumtoxinA) neurotoxin does not permanently alter the neuromuscular junction.
در اين صفحه سعي دارم تا با جديدترين اطلاعات علمي در زمينه هاي كازمتيك، پوست و مو و همچنين بيان نظرات شخصي در خدمت عزيزان باشم . اميدوارم مورد قبول واقع گردد . دكتر محمد بقايي